I think the actual world standard is what my airline does (and many others) and is what I (as company policy) always brief the crew on before each sector:
Light (annoying) turbulence: Seat Belt sign ON and cabin attendants check compliance and continue whatever level of service the Purser is happy with.
Moderate or more turbulence: Seat Belt sign cycled 2 times and PA "This is the Captain speaking, could all cabin attendants please take their seats". This requires an immediate response.
Fact is the Cabin Crew being both trained and experienced can walk around in light turbulence conditions we don't want the SLF doing. But if it gets worse (or if the Purser requests it) we shut up shop for the duration.
How much simpler could it be? By the way, all the cabin crew I fly with enjoy going to work. Barely a missed smile from start-up to shut down. Wonderful!